This invention relates to a liquid-supply system, and more particularly to an anti-hammer device usable in such a system where liquids from two conduit streams are pulse-blended, and merged into a single output stream. The invention, while having clear applicability in a number of different settings, is described hereinbelow in connection with a film-processing, liquid-temperature-control system in which it has been found to offer particular utility.
By way of illustration, recently proposed for use in various film-processing machines is a system which, in recurrent pulses, alternately blends hot and cold water (from a conventional water-supply system) into a single temperature-controlled output stream. A full disclosure of this system is found in our copending U.S. patent application, Ser. No. 347,103, filed Feb. 19, 1982, for "DIFFERING-TEMPERATURE WATER-MIXING APPARATUS AND METHOD USING PULSED, DUTY-CYCLE TEMPERATURE CONTROL". In this system, as well as in other kinds of two-liquid pulse-blending systems, the quick-response alternate "shut-offs" of liquid flow in the two liquid input conduits presents a serious, and potentially quite irritating and damaging, liquid-hammer condition in the upstream plumbing.
A general object of the present invention is to provide a unique anti-hammer device usable in a two-liquid-stream plumbing system to eliminate substantially all hammer effects in both upstream conduits in the system.
According to a preferred embodiment of the invention, the anti-hammer device takes the form of a split housing which is separated by a flexible diaphragm into two liquid-receiving plenums. Each plenum is connected to a different one of the two liquid-supply conduits in a plumbing system-upstream from where valving, for flow control, takes place. When liquid flow in one conduit is shut off, and flow in the other is started, the diaphragm flexes instantly away from that plenum in the device which is connected to the "shut-off" conduit due to the instantaneous pressure differential created. This action, utilizing the lower-pressure liquid condition in the "flowing" side of the system, absorbs "shut-off" shock, and prevents hammer in the associated conduit. The diaphragm flexes in the opposite direction when flow in the "other" conduit is stopped, and flow in the "one" conduit begun.